The subject matter of the present invention is a linear actuator for gates, doors and other similar passage barriers with at least one closing wing or the like swinging around a generally virtually vertical oscillation axis and comprising an articulated actuator arm with its rear end articulated to a fixed support in a manner swinging around a traversing axis virtually parallel to the oscillation axis of the wing and near it with there being assembled in the actuator arm an irreversible handling pair consisting of a screw and a respective nut and a nutscrew of which the screw extends in the longitudinal direction of the actuator arm and is operated at its rear end by an electric motor and by a reduction gear assembled in the actuator arm while the nutscrew slides along the actuator arm and is articulated to the wing or to a part fastened to the wing in a manner rotating around an articulation axis virtually parallel to the oscillation axis of the wing. DE-A-19640227 discloses a linear actuator wherein the gate wing can be manually moved in case of the motor not working, thanks to a locking means which can be released in order to allow the actuator arm to rotate independently from the gate wing. However, the actuator arm and the gate wing remain connected to each other.
The general purpose of the present invention is to improve the above mentioned type of linear actuator so as to obtain in combination with a simple, economical and reliable construction embodiment the possibility of easy assembly and safe operation of the actuator within broad geometrical tolerances for example even in the case of imperfect parallelism between the oscillation axis of the wing and/or the traversing axis of the actuator arm and/or the articulation axis of the nutscrew to the wing together with the possibility of disengaging the actuator arm in an emergency for example power failure with easy and fast operation of the respective wing so as to be able to move the wing manually and in particular even in its closed position.
The purpose is achieved by the present invention having the following characteristics.
(a) The actuator arm is articulated to the fixed support by means of a joint allowing in addition to oscillation of the actuator arm around the traversing axis a vertical angular shifting of said arm upward around an inclination axis virtually horizontal and transversal to the actuator, and
(b) the nutscrew is articulated to the wing by means of a joint allowing disengagement of the nutscrew from the wing by means of a vertical angular shift upward of the actuator arm around its inclination axis.
Preferably in accordance with a preferred embodiment the linear actuator in accordance with the present invention also has the following characteristics.
(c) There are provided movable stop means operated and/or born by the nutscrew or by the shiftable parts together therewith and in particular by parts integral with the wing and said movable stop means automatically engage in the forward end position of the nutscrew corresponding to the closed position of the wing with associated stop means born by the actuator arm so as to prevent angular upward shifting of the actuator arm around its inclination axis, and
(d) the forward end of the screw opposite the operating motor is accessible at the respective free end of the actuator arm and can be coupled with manual rotation means with the aid of which it can be rotated in an emergency in such a manner as to shift the nutscrew from its closed front end position of the wing backward towards its rear end and by an amount such as to disengage the movable stop means from the stop means born by the actuator arm and thus allow angular shifting upward of the actuator arm around its inclination axis so as to disengage the nutscrew and hence the actuator arm from the wing and allow manual shifting thereof.
Both the joint between the actuator arm and its support and the joint between the nutscrew and the wing can be made in any manner suited to the purpose. In accordance with a preferred embodiment the joint between the actuator arm and its support consists of a ball joint or a universal joint with two axes, viz made up of two cylindrical articulations at a right angle to each other with one having an axis virtually horizontal and transversal to the actuator arm (actuator arm inclination axis) and the other with virtually vertical axis (actuator arm traversing axis).
The joint between the nutscrew and the wing in accordance with a preferred embodiment can be a two-axis universal joint, viz a joint made up of two cylindrical articulations with axes at right angles to each other with one having an axis virtually horizontal and transversal to the actuator arm (directional axis) between the nutscrew and a leadnut holder member and the other with virtually vertical axis (articulation axis) provided between the leadnut holder and the wing provided in a manner disengageable from the wing by upward shifting of the actuator arm around its inclination axis. In particular said two-axis universal joint consists of a leadnut holder member provided below with a cylindrical articulation pivot with axis virtually parallel to the wing oscillation pivot, viz generally virtually vertical with said articulation pivot engaging in a manner turning around its axis in a corresponding articulation bush integral with the wing and withdrawable upward from said bush or vice versa while the nutscrew is assembled in the leadnut holder so as to turn around a directional axis virtually horizontal to and transversal to the actuator arm, viz virtually parallel to the actuator arm inclination axis.
The stop means between the actuator arm and the nutscrew and/or the wing at the end of travel of the latter for closing the wing can be made in various ways. In accordance with a very simple and economical embodiment the stop means consist of at least one movable stop projection which is integral with the nutscrew or the leadnut holder or the wing and which automatically engages at the end of the nutscrew closing travel in a corresponding stop recess provided in the actuator arm or vice versa.
The manual emergency screw operation means can also be made in any manner suited to the purpose in order to move the nutscrew backwards and consequently release the actuator arm to allow moving it angularly upward. In accordance with a preferred embodiment said manual emergency operating means consist of an axial head hole provided in the accessible front end of the screw and having a not round profile and corresponding if necessary to a given coding and a release key having a tang with cross section correspondingly profiled and engageable in said screw head hole or vice versa.